This invention relates to a new and improved helical-scan video tape recorder (VTR), in which a magnetic tape is scanned at an angle with respect to the longitudinal direction of the tape to form a slanted track or record thereon, and more particularly to such a device having a tape-loosening mechanism.
Ordinarily, in a helical-scan VTR, when a running magnetic tape is brought to a stop, it is held tightly under tension and remains in engagement with the peripheral surfaces of adjacent component parts such as guide posts, a stationary head and a guide drum. The tape may thus occasionally adhere to the contacting component surfaces due to a type of vacuum condition to which the contacting ares are subjected or due to dew formation in the narrow air spaces or layers surrounding the contacting areas. Particularly, in the event of dew formation, when the dew once deposited evaporates, the tape adhesion may be enhanced to such an extent that the tape sticks tightly to the adjacent component surfaces. Such sticking phenomenon of the magnetic tape is likely to occur particularly on the outer peripheral surface of the guide drum or a similar component surface with which the tape is placed in contact along a substantial and continuous length thereof. If the magnetic tape is driven and starts running while adhering to the adjacent component or components or while deposits of dew are present, it will be subjected to unduly large tensioning because of the adhesion and in some cases it will fail to start, remaining stuck to the contacting component surfaces. Thus, the phenomenon of tape sticking materially impairs the operational performance required of a helical-scan VTR.
Accordingly, it is an object of the present invention to provide a helical-scan VTR having a tape-loosening mechanism designed to prevent any tape-sticking phenomenon which may occur along the contacting surface of the magnetic tape.